The present invention relates more particularly, but not exclusively, to a type of dispenser member that is commonly known as a “pusher-pump”. Such a term is explained by the fact that the dispenser member includes a pusher that forms not only a dispenser orifice, but also defines a portion of a fluid chamber in which the fluid is put under pressure in selective manner. For a pump, said portion is a pump chamber. A distinctive feature of that pusher-pump resides in the fact that an inside surface of the pusher, of generally substantially cylindrical shape, serves as a sealing slide-cylinder for a piston that moves with leaktight contact inside the cylinder, thereby opening and closing an outlet valve. In general, the piston is a piston of the differential type that moves in response to a variation in the pressure of the fluid inside the chamber.
Such a fluid dispenser member of the pusher-pump type is known in particular from document WO 2005/084820. The dispenser member is specially adapted to fluids that are not very viscous, such as perfumes, and that are desirably dispensed in the form of a spray. The dispenser member in that document is not adapted in any way to dispensing viscous fluids such as creams or gels that are generally dispensed in the form of streams or knobs. The piston of the differential type includes a first valve lip that slides in leaktight manner in a cylinder formed by the pusher, and a second lip that is engaged in another cylinder, referred to as a “main” cylinder, formed by the body of the dispenser member. The lip in sliding contact in the pusher can be referred to by the term “differential lip” or “outlet valve”, whereas the lip that slides in leaktight manner in the main cylinder of the body can be referred to by the term “main lip”. In addition, the pusher includes a dispenser orifice upstream from which there is formed a swirl system that is provided in the form of tangential channels that connect to a central swirl chamber that is centered on the dispenser orifice. The outlet valve is not formed directly by the valve lip, but by a small ring that extends the valve lip, and that is for coming into leaktight bearing contact against an outlet-valve seat of frustoconical shape. By displacing the differential piston relative to the pusher, the leaktight contact between the valve ring and its frustoconical seat is broken, and the fluid that has been put under pressure in the pump chamber of the dispenser member can thus escape towards the swirl system and the dispenser orifice. The fluid is prevented from escaping, or, more precisely, is constrained to be dispensed through the dispenser orifice as a result of the presence of the leaktight contact between the valve lip and the inside of the pusher forming the slide cylinder.
As explained, the above-mentioned document is particularly adapted to dispensing perfume. When it is desired to dispense viscous fluids such as creams, pastes, or gels, it is necessary to reduce, as much as possible, the degree to which the fluid to be dispensed comes into contact with the outside air, which can deteriorate the fluid by oxidization or by drying out. In the above-mentioned prior-art dispenser member, the fluid that is downstream from the outlet valve communicates with the outside through the dispenser orifice. This applies in particular for the fluid that is stored in the swirl system, namely in the tangential channels and in the central chamber. This is not acceptable for a dispenser member for dispensing fluids such as creams, pastes, or gels.
It is for example known from U.S. Pat. No. 4,511,064 a pump comprising a piston sliding against an inside surface of a dispenser wall forming a dispensing spout extending laterally. The spout forms an inner duct ending with a dispensing orifice. The piston closes at rest the inlet of the inner duct. The inside surface is cylindrical, so that the piston has to move on a determined distance before opening the inlet of the duct. This provides a precompression of the fluid product, which is thus expelled through the inner duct with a great pressure. This is no desired when dispensing viscous products, such as creams, pastes or gels. In fact, the product must not be projected out of the dispensing orifice. On the contrary, it must form a nut or a large droplet which is easily collectable by the user.